Drawing lead sharpener

ABSTRACT

This invention relates to an improved power operated drawing lead sharpener used for sharpening the drawing leads for mechanical drafting operations. The specification discloses an improved cutting head mechanism wherein multiple cutting blades insertable in a carrier member form a replaceable cartridge which is inserted in the cutting head. Therefore, the draftsman can service the unit himself which was not possible previously. Also, there is disclosed an improved swivel mounting for the cutting head whereby while the cutter head is easily removed for emptying the graphite particles produced by the sharpening process, it cannot fall off accidentally.

I Umted States Patent 1191 1111 3,776,286

Blanck 1 Dec. 4, 1973 DRAWING LEAD SHARPENER [76] Inventor: chimes M. Blanck, 1545 State, f 'f'{ has! Algonac Mich 48001 Assistant ExammerJames F. Coan Attorney-Gregory S. Dolgorukov [22] Filed: Mar. 6, 1972 [21] Appl. No.: 231,861 [57] ABSTRACT This invention relates to an improved power operated [52] US. Cl. 144/285, 144/28.72 drawing lead sharpener used for sharpening the draw- [51] Int. Cl. B43! 23/02 ing leads for mechanical drafting operations. The [58] Field of Search... 144/281, 28.3, 28.4, specification discloses an improved cutting head 144/286, 28.72, 28.8, 28.9, 28.5 mechanism wherein multiple cutting blades insertable in a carrier member form a replaceable cartridge [56] References Cited which is inserted in the cutting head. Therefore, the UNITED STATES PATENTS draftsman can service the unit himself which was not 3 424210 H969 Dziuk et al 144/28 72 possible previously. Also, there is disclosed an im- 2372900 2/1959 Men 144/2255 proved swivel mounting for the cutting head whereby 3:595:285 7/1971 Rubenm 144/2872 while the cutter head is easily removed for emptying 3,090,358 5/1963 Condon 144/28.72 the graphite Particles Produced y the Sharpening P 2,9l4,030 11/1959 Behrens 144/285 X cess, it cannot fall off accidentally. 3,104,535 9/1963 Kent 144/286 x 1 3,175,539 3/1965 Saflund et a1 144 285 x 9 Chums, 6 Drawmg Flgul'es 'q- 'f r r 1 1 L Q J r .2 i "1? E it 1' 1 l 'L i- .:J

1 i 21 t 1" I, l ,A 1. 1 .33 :5 a" '3 l} 1 I l DRAWING LEAD SI-IARPENER This invention relates to a power operated device for sharpening any of the several types of drawing leads that may be used in various drafting operations, such as compass leads and leads found in mechanical drafting pencils. Although the medium drawing the line is graphite, because of long usage or inertia, this part of the pencil is called lead, and it will be understood that hereinafter by the term lead" is meant a thin graphite rod, usually of the circular cross section.

Mechanical drafting pencils are now preferred by most draftsmen for general drafting use over the old wood sheathed drawing pencils. These mechanical drawing pencils allow the drawing lead, i.e. the thin graphite bar, to be extended any desired distance while in use. Therefore, since it is just the drawing lead itself.

which needs to be sharpened and there is no wood to cut away in the sharpening process, the many types of sharpeners available for the old wood sheathed drawing pencils cannot be used for mechanical drawing pencils.

In view of this, several attempts have been made in the prior art to devise a workable drawing lead pointer for these mechanical pencils.

One such device consists of a rotating sand paper disc and apparatus to hold the drawing lead against it at a desired angle while the pencil is manually turned.

Another such device attempted to adopt the rotary cutters used for wood sheathed drawing pencils to sharpen mechanical drawing leads. However, this device is very bulky and has a tendency to snap off the lead which it is trying to sharpen.

One of the most recent devices is disclosed in a patent to H. Merz entitled, Power Operated Drawing- Lead Sharpener bearing the U.S. Pat. No. 2,872,900. However, even this device leaves several problems unanswered in the search to find a satisfactory drawing lead pointer. First of all it is still rather bulky. Its rectangular shape makes it inconvenient to handle. Also, the Merz pencil sharpener has a rather unstable cutting action since the cutting takes place only on one side of the lead, and the lead being directed toward this one side all the time produces a force on the cutter head away from the center line thereof, encouraging the cutter head to startoscillating and possibly to snap the lead. In combination with this, after a short period of use the graphite drawing lead will wear out a depression -in the ball member on which said cutter head is mounted since the graphite is an abrasive material. Since the graphite drawing lead is free to communicate with the top surface of the supporting ball member, when the depression in the top of said ball member becomes deep enough, the entrapping of the drawing lead point in this depression coupled with the natural tendency of the cutting head to rotate off center can combine and snap the drawing lead. The felt bushing shown in the Merz patent, although it ultimately limits the amount of unstable rotation, does nothing to stabilize the cutting head.

Another disadvantage of a device of this general nature is the fact that the user cannot service the cutter head himself since the location of the cutting blade inside the cutter head of the sharpener is critical, and there is no way to locate it after disturbing it except by a special jig. This leads to relatively frequent and expensive servicing of the unit.

Accordingly, it is an object of the present invention to provide a power operated drawing lead pointer having a replaceable cutter cartridge which is supplied by the manufacturer and can be easily and inexpensively replaced by the customer himself.

A further object of the present invention is to provide multiple cutting blades arranged radially about the axis of the drawing lead being pointed so that there are no uneven forces being produced which would promote an unstable action of the cutter head.

A further object of the invention is to provide a cutter head assembly in which the tip of the lead being pointed cannot contact the cutting head supporting member.

A still further object of the present invention is to provide a drawing lead pointer having a spring loaded bushing surrounding the cutter head assembly in such a manner that the cutter head will swivel enough to compensate for the situation in which the drawing lead is inserted at an angle, but which will constrain the cutting head sufficiently so as not to allow any unstable motion of said cutting head caused by the operator to become unmanageable.

- A still further object of the invention is to provide a power operated drawing lead sharpener contained in a circular case for ease of manufacture and handling.

Another object of the invention is to provide suitable means to retain the cutting head on its supporting member so that it does not easily fall off if the sharpener is accidently upset, but which can be removed without difficulty for emptying the accumulated graphite from the drawing lead sharpener.

Further objects and advantages of this invention will be apparent from the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification, wherein like reference characters designate corresponding parts in the several views.

FIG. 1 is a plan view of the drawing lead pointer embodying the present invention.

FIG. 2 is a sectional view taken in the direction of the arrows on the section line 2-2 of FIG. 1.

FIG. 3 is an enlarged sectional] view of the cutting head and ball shaped supporting member, taken in the direction of the arrows on the section line 22 of FIG.

FIG. 4 is an enarged cutaway view showing the switch mechanism intended to start and stop the sharpener.

FIG. 5 is an elevational view of the removeable cutter cartridge which is insertable into the cutting head for use.

FIG. 6 is a top view of the construction of FIG. 5, showing the arrangement of the multiple cutter blades.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways within the scope of the claims. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.

The drawing head pointer embodying the present invention comprises a housing 10 having a top wall 23 and depending side walls, and having a post 11 provided substantially in the middle thereof being held in place by a screw 12. A spring clip 13 cooperates with the post 1 1 to define an area suitable for the accomodation of four ordinary size D flashlight batteries 14. To

retain said batteries in place, a retaining member fits over the post 11 and is held in place by the cotter pin 16. Suitable contacts 17 and electrical conductors 18 are provided so that the batteries may be electrically connected with a small electric motor 19 through a switch mechanism generally designated by the numeral The motor 19 is connected to the underside of a collecting pan 21 which in turn is connected through a circular contact carrier 22 to the top wall 23 of the housing. The collecting pan 21 is so shaped as to define a space for the collection of graphite powder between its inner wall and part of the surface of the contact carrier 22. The remainder of the contact carrier has contacts suitable to interconnect the batteries 14 mounted thereon. The motor 19 and a suitable switch mechanism are fastened to the underside of the collecting pan 21 by suitable fastening means generally designated by the numeral 25.

The upper end 29 of the motor shaft 26 extends into the space defined by the inner wall of the collecting pan 21 and the contact carrier 22. Said upper end 29 of the motor shaft 26 is provided with a supporting member 32 having an upper ball shaped portion 33, see FIG. 3, having two axially and radially extending slots 34 provided therein and a lower portion 35 adapted to be press fit on the upper end of the motor shaft 29.

The lower end 30 of the motor shaft 26 is in contact with an electrically conducting spring contact 36 which is positioned adjacent to a rigid contact 37. As explained later, when pressure is put on the motor shaft 26 causing it to move in a downward direction, the spring contact 36 is contacted by the lower end 30 of the motor shaft 26 and is forced to contact the rigid contact 37, thereby completing an electrical circuit and supplying current for the operation of the electric motor 19.

Referring specifically to FIGS. 3-6, the cutting head generally designated by the numeral 40 consists of an upper portion 41 provided with a hole in the top thereof and with a plurality of axially extending slots 43. The slots 43 serve to provide for discharge of the graphite particles produced in the sharpening process. The inner wall 45 of said upper portion 41 is provided with a downwardly and outwardly extending taper.

A cutting cartridge 46 is adapted to hold four axially and radially extending cutting blades 47 in such a manner that their inner edges 48 define the shape of point to be obtained on the drawing lead 49, and also in such a way that the shape defined will be symetrical about the axis of the cutter cartridge which under normal operating conditions will be symetrical about the axis of the motor shaft 26, and the space defined by the said inner edges 48 will be directly beneath an opening 42 provided in the top of said cutter cartridge 46, and along said axis. The cutting cartridge is so made that when it is inserted in the upper portion of the cutting head 41, the opening 50 in the cutting cartridge 46 will be directly beneath the hole 42 in said cutting cartridge 40 and the outer edges 52 of the cutting blades 47 come into substantially complete contact with the inner wall 45 of the upper portion of the cutting head 41, thereby preventing any movement of the cutting blades 47 when they are in place in the cutting head 40.

it can now be seen that by virtue of the abovedescribed construction an easily replaceable cutting cartridge can be used by the customer to service the unit himself since the position of the cutting blades is always firmly established through contact with the tapered inner wall of the cutting head. No expensive jig for servicing is required and, therefore, no servicing of the cutter head by the manufacturer only should ever be required. Also, it can be seen that since balanced forces are being exerted on the drawing lead, the shape of the blades can be such as to provide for almost any shape point on the drawing lead which may be desired. This would not be possible with only one cutting blade.

An additional advantage of my improved drawing lead sharpener is that it sharpens regardless of whether the cutting head 40 is rotating clockwise or counterclockwise. This results from the fact that the inner edge 48 of the blade 47 is ground square to produce two cutting edges 48a and 48b. Since only one of the two edges of each blade will be cutting at any one time depending on the direction of rotation of the cutter head, when the blades 47 start to get dull, it is only necessary to reverse the polarity of the batteries 14 to expose a sharp edge to the graphite lead 49. Since the life of the blade is effectively doubled over the old single edged blade, the maintenance of the sharpener is still further reduced.

The cutting cartridge 46 is held in the upper portion of the cutting head 41 by a lower portion 53 thereof adapted to close the open end of the cutting head 40. Said lower portion 53 is provided with a bore 54 adapted to fit over the ball shaped portion 33 of the supporting member 32. Extending into the bore 54 is a driving pin 55 adapted to drivingly engage one of the slots 34 in the supporting member 32. Also provided in the lower portion of the cutting head 53 is a ball and spring retaining mechanism generally designated by the numeral 56 which extends into the bore 54 to engage the ball shaped portion 33 of the supporting member 32 at a position other than where one of the slots 34 is provided and thereby prevent the cutting head from coming off easily when the drawing lead pointer is upset, but being relatively easily removeable when necessary to empty the graphite powder from the collecting pan 21.

In use the cutting head is placed over the supporting member 32 and extends through holes provided in the contact carrier 22 and in the housing 10. A recessed portion 31 is provided in the opening of the housing 10 in such a manner that a coil spring 28 and bushing 27 fit in the space between the contact carrier 22 and the inner surface of the top wall 23.

The slight pressure exerted on the bushing 27 by the spring 28 serves to keep the cutter head from being misaligned. If too great a misalignment of the cutter head 40 is caused by the operator so that the bushing slips too far, the cutting head 40 will come into contact with the coils of the spring 28 and be further restrained in this manner.

As downward pressure is exerted on the cutting head '40, it is transmitted through the supporting member 32 to the motor shaft 26. This downward pressure causes the motor shaft 26 to move downward a sufficient amount to cause the spring contact 36 to come into electrical contact with the rigid contact 37, completing the electrical circuit and thereby starting the electric motor 19 and causing the cutting head 40 to begin the sharpening process. As the drawing lead is pointed, the load on the sharpening assembly becomes less and less. Finally, when the sharpening process is completed,

there is no load on the electric motor 19. The operator can tell this condition by the sound the electric motor makes when it occurs. Hearing this, the operator will remove the lead being sharpened, which will release the downward pressure on the motor shaft 26, causing the spring contact 36 to move out of engagement with the rigid contact 37, thereby stopping the sharpening process.

After a number of sharpenings, the collecting pan 21 will become full of graphite particles and will need to be emptied. In order to achieve this, it is only necessary to grasp the cutting head 40 and to apply a slight upward pressure thereon in order to force the ball and spring mechanism 56 inward and thereby release said cutting head 40 from the supporting head 32 and allow its removal. Once the cutting head is removed, it is only necessary to grasp the sharpener, turn it over, and shake out the graphite particles.

After a long period of use, the batteries 14 in the sharpener will need replacing. In order to do this, it is only necessary to remove the cotter pin 16 from the post 1 1, lift off the retainer member 15, and remove the batteries. Replacing the batteries merely involves the reverse operation.

As can be seen from the foregoing description, a drawing lead sharpener which is easily serviceable and which has an inherently stable cutting action is provided.

By virtue of the above-described construction the objects of the invention listed above and numerous additional advantages are attained.

I claim:

1. A sharpener for drawing leads, comprising a housing having top and side walls, an opening provided in said top wall, a collector member fastened to the underside of said top wall under the opening to enclose a suitable space to collect particles produced by the sharpening process, a driving means mounted on the underside of said collector member with the upper end of its shaft extending into the space enclosed by said collector member, a supporting member mounted on the upper end of said shaft, a cutter head having multiple removable cutting blades swivelly mounted on said supporting member in such a manner that said drawing lead, when inserted, can not contact said support member, said cutter head extending through the opening provided in the top wall of said housing and drivingly but removably connected to said supporting member, cutter head restraining means mounted in the opening in said top wall and cooperating with said cutter head to limit the swivelling motion of said cutter head, and switch means to automatically start said driving means when said drawing lead is inserted.

2. A sharpener for drawing leads, comprising a housing having top and side walls, an opening provided in said top wall, a collector member fastened to the underside of said top wall under the opening to enclose a suitable space to collect particles produced by the sharpening process, a driving means mounted on the underside of said collector member-with the upper end of its shaft extending into the space enclosed by said collector member, a supporting member mounted on the upper end of said shaft and having at least one slot therein, a cutter head swivelly mounted on said supporting member and extending through the opening provided in the top wall and drivingly but removably connected thereto, cutter head restraining means mounted in the opening in said top wall and cooperating with said cutter head to limit the swivelling motion of said cutter head, and switch means to automatically start driving means when said drawing lead is inserted, wherein said cutter head includes an upper portion comprising a hollow cylinder having a tapered inner surface and being closed at the top thereof, and provided with an opening in the top to receive a drawing lead, a cutting cartridge adapted to receive multiple radially and axially extending blades, such that the inner cutting edges of said blades form the desired point on the lead, and the outer edges contact the tapered inner wall of said upper part and are securely retained in the cutting cartridge when inserted therein, multiple cutter blades inserted in said cutting cartridge, and a lower portion adapted to close the open end of said upper portion, thereby retaining said cutter cartridge, said lower portion having a bore therethrough to provide a discharge for the graphite particles produced by the cutter blades, said bore also being complimentary in shape to said supporting member to swivelly support said cutter head thereon, and a pin inserted in said bore to drivingly engage the slot in said supporting member to drive said cutter.

3. The device defined in claim 2, wherein said supporting member has an upper hemispherical shape portion and a lower cylindrically shaped mounting portion, said upper portion having at least. one radially and axially extending slot provided therein.

4. The device defined in claim 2, wherein said supporting member has an upper hemispherical shaped portion and a lower cylindrical shaped mounting portion, said upper portion having two perpendicular radially and axially extending slots therein.

5. The device defined in claim 2, wherein the upper portion of said cutting head is provided with multiple axially extending slots in the side wall thereof for discharge of the graphite particles produced during the sharpening process.

6. The device defined in claim 3, and including a ball and spring retaining device adapted to engage the lower portion of the hemispherical part of the supporting member to prevent said cutting head from falling off, should the sharpener be upset in use.

7. The device defined in claim 2, wherein said housing has a circular cross-section.

8. The device defined in claim 2, wherein said drive means are in the form of an electric motor.

9. The device defined in claim 8, wherein said switch means are in the form of a spring contact, communicating with and driven by the movement of the motor shaft into and out of electrical contact with a rigid contact. 

1. A sharpener for drawing leads, comprising a housing having top and side walls, an opening provided in said top wall, a collector member fastened to the underside of said top wall under the opening to enclose a suitable space to collect particles produced by the sharpening process, a driving means mounted on the underside of said collector member with the upper end of its shaft extending into the space enclosed by said collector member, a supporting member mounted on the upper end of said shaft, a cutter head having multiple removable cutting blades swivelly mounted on said supporting member in such a manner that said drawing lead, when inserted, can not contact said support member, said cutter head extending through the opening provided in the top wall of said housing and drivingly but removably connected to said supporting member, cutter head restraining means mounted in the opening in said top wall and cooperating with said cutter head to limit the swivelling motion of said cutter head, and switch means to automatically start said driving means when said drawing lead is inserted.
 2. A sharpener for drawing leads, comprising a housing having top and side walls, an opening provided in said top wall, a collector member fastened to the underside of said top wall under the opening to enclose a suitable space to collect particles produced by the sharpening process, a driving means mounted on the underside of said collector member with the upper end of its shaft extending into the space enclosed by said collector member, a supporting member mounted on the upper end of said shaft and having at least one slot therein, a cutter head swivelly mounted on said supporting member and extending through the opening provided in the top wall and drivingly but removably connected thereto, cutter head restraining means mounted in the opening in said top wall and cooperating with said cutter head to limit the swivelling motion of said cutter head, and switch means to automatically start driving means when said drawing lead is inserted, wherein said cutter head includes an upper portion comprising a hollow cylinder having a tapered inner surface and being closed at the top thereof, and provided with an opening in the top to receive a drawing lead, a cutting cartridge adapted to receive multiple radially and axially extending blades, such that the inner cutting edges of said blades form the desired point on the lead, and the outer edges contact the tapered inner wall of said upper part and are securely retained in the cutting cartridge when inserted therein, multiple cutter blades inserted in said cutting cartridge, and a lower portion adapted to close the open end of said upper portion, thereby retaining said cutter cartridge, said lower portion having a bore therethrough to provide a discharge for the graphite particles produced by the cutter blades, said bore also being complimentary in shape to said supporting member to swivelly support said cutter head thereon, and a pin inserted in said bore to drivingly engage the slot in said supporting member to drive said cutter.
 3. The device defined in claim 2, wherein said supporting member has an upper hemispherical shape portion and a lower cylindrically shaped mounting portion, said upper portion having at least one radially and axially eXtending slot provided therein.
 4. The device defined in claim 2, wherein said supporting member has an upper hemispherical shaped portion and a lower cylindrical shaped mounting portion, said upper portion having two perpendicular radially and axially extending slots therein.
 5. The device defined in claim 2, wherein the upper portion of said cutting head is provided with multiple axially extending slots in the side wall thereof for discharge of the graphite particles produced during the sharpening process.
 6. The device defined in claim 3, and including a ball and spring retaining device adapted to engage the lower portion of the hemispherical part of the supporting member to prevent said cutting head from falling off, should the sharpener be upset in use.
 7. The device defined in claim 2, wherein said housing has a circular cross-section.
 8. The device defined in claim 2, wherein said drive means are in the form of an electric motor.
 9. The device defined in claim 8, wherein said switch means are in the form of a spring contact, communicating with and driven by the movement of the motor shaft into and out of electrical contact with a rigid contact. 